Stress in the left ventricular wall during isobaric contractions and biaxial stress-strain relation of the unit cardiac muscle fiber.

Abstract

Stress distribution in the left ventricular wall during isobaric contractions was determined analytically from the pressure-volume relationship based on the large deformation theory by assuming spherical geometry of the left ventricles. Numerical results from experiments using 4 dogs showed that the hoop strain decreased with time during isobaric contractions, while the hoop stress decreased at first, and then increased after the minimum value. A mechanical model of the unit cardiac muscle fiber was obtained. Based on this model, it was found that the biaxial stress-strain relation of the unit cardiac muscle fiber during isotonic contractions changed with the muscle length at rest, and it was expressed by different curves, depending on the muscle contractions.